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Introduction Chemical immobilization is the use of drugs to capture or restrain animals. The term “immobilization” describes the actions of such drugs which can range from tranquilization to paralysis to general anesthesia.

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Considerations-Questions ► What is the species, age, sex, and physical condition of the animals being captured? ► What need to be done with or to the animals while they are restrained? ► Is physical restraint or chemical immobilization the better option? ► Is adequate assistance available? ► Is the proper equipment available? ► What is the local geography and landcover like? ► What is the local weather on the capture days?

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Characteristics of Ideal Immobilizing Drug ► Wide safety margin for a given dosage ► Compatible with other drugs and solutions ► No adverse tissue reaction if administered intramuscularly ► Short induction time ► Should be reversible (with an antagonist or antidote) ► Chemically stable ► Concentrated to allow small volume dosage (~2–3ml) ► Low cost ► Not a controlled substance

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Legal Considerations ► Conditions for the use of drugs (pharmaceuticals) are established by the Food and Drug Administration (FDA). Only 4 drugs have been specifically approved by the FDA for use on certain wild animals: carfentanil for use on cervids; xylazine for use on elk and fallow, mule, sika, and white-tailed deer; yohimbine for use on cervids (deer and elk); and ketamine for use on primates. ► However, the Animal Medicinal Drug Use Clarification Act of 1994 essentially allowed approved animal and human drugs to be used “extra label” under certain conditions. In general, those conditions are the drug: (1) approved by the FDA; (2) used by, or on the lawful written or oral order of, a licensed veterinarian; and (3) used within the context of a valid veterinarian/client/patient relationship.

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Additional Legal Considerations ► Additionally, if the animal could be consumed by a human, the veterinarian should: (1) establish a substantially extended withdrawal time (the time from the date that a drug was administered to when the animal can safely be consumed by humans); (2) be able to identify the treated animals; and (3) assure that assigned timeframes for withdrawal are met and no illegal residues occur.

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Controlled Substances A controlled substance means a drug that is identified in 1 of 5 schedules established by the Drug Enforcement Administration (DEA). Special regulations govern the recording and storage of these drugs. Act requires an individual to have a special DEA registration number in order to possess controlled substances. Biologists have obtained a DEA registration number and have been able to procure drugs through veterinary product distributors. However, even though they are in possession of these drugs, they cannot use them on animals without veterinary supervision. Non- veterinarians can legally administer drugs if a valid veterinarian/client/patient relationship is established. The veterinarian does not have to be on site during the actual immobilization event, but he or she should be involved in the planning process.

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Drug Schedules Schedule I: This is reserved for experimental and abused drugs such as heroin, marijuana, and lysergic acid diethylamide (LSD). No capture drugs are Schedule I. Schedule II (IIN): This includes most of the opioids used for animal immobilization, such as etorphine, fentanyl, sufentanil, and carfentanil and the opioid antagonist, diprenorphine. Schedule III (IIIN): This contains ketamine and tiletamine/zolazepam. Schedule IV: Includes benzodiazepine tranquilizers, such as diazepam and midazolam, and butorphanol. Schedule V: This covers small, limited quantities of narcotic drugs included in preparations with non-narcotic active medicinal ingredients. No capture drugs are Schedule V.

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Types of Drugs Used: Dissociative Anesthetics  Ketamine hydrochloride (Ketaset®, Vetalar®) ► Wide margin of safety ► Used with a wide variety of animals ► Often used with xylazine or acetylpromazine ► Produces catatonia-like immobilization ► Reversible with tolazoline (Priscoline®) ► Readily available ► May need large volumes for some species  Tiletamine and zolazepam (Telazol®) ► Zolazepam is a tranquilizer, so no others needed ► Wide margin of safety ► Used with a wide variety of animals ► Federal permit required; Schedule III controlled substance; must be under the authority of licensed veterinarian  Phencyclidine hydrochloride (Sernylan®) ► Wide margin of safety ► Was the agent of choice for large carnivores (e.g., Ursus spp.) ► Can be combined with tranquilizers ► Not readily available; Schedule II controlled substance; must be under the authority of licensed veterinarian ► Compound also known as PCP or "angel-dust" ► Human abuse potential

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Types of Drugs Used: Narcotic Anesthetics  Not readily available, controlled substances  Significant risk to humans  Used on a wide variety of animals, especially ungulates  Can be used with other agents  Reversible with naloxone (Naline®) or specific antagonists  Examples ► Etorphine (M-99®)  Readily reversible with diprenorphine (M- 50/50®)  May require larger volumes in mega- herbivores  Often used with xylazine  Available with acepromazine as Large and Small Animal Immobilon®  Schedule II controlled substance; must be under the authority of licensed veterinarian Fentanyl  Often combined with droperidol (Innovar-Vet®)  Readily reversible with naloxone  Schedule II controlled substance; must be under the authority of licensed veterinarian ► Carfentanil citrate (Wildnil®)  Works well on the largest animals  Readily reversible with naloxone  Schedule II controlled substance; must be under the authority of licensed veterinarian  Extremely dangerous for humans if accidentally exposed

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Dart Placement The preferred areas for intramuscular injection are the large muscles of the hindquarters or the shoulder. In elk and many other ungulates, the area in the rump where the light hair meets the darker hair is a good aiming point.

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Moose immobilized with only opioids (carfentanil, thiafentanil, etorphine) invariably remain sternal with head up. The addition of a tranquilizer increases the probability of pneumonia because moose have a tendency to roll over and aspirate rumen contents.

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SUMMARY ► Drugs and the equipment used to administer them have become more sophisticated, efficacious, and safe over the past half century. ► Today, capture drugs should be part of every wildlife management professional’s armamentarium. ► Although capture drugs should be used judiciously, they should always be considered as a primary solution to should always be considered as a primary solution to problems where animal and human safety is uppermost. problems where animal and human safety is uppermost.